#include <iostream>

using namespace std;

const int N = 100010;

int m;
int stk[N],tt;
int main(){
    cin >> m;
    while(m --){
        string op;
        int x;
        cin >> op;
        if(op == "push"){
            cin>>x;
            stk[++tt] = x;
        }
        else if(op == "pop") tt -- ;
        else if(op == "empty") cout << (tt?"NO" : "YES") << endl;
        else cout << stk[tt] << endl;
    }

    return 0;

}